A fuel cell system includes one or more fuel cell modules, which in turn include a number of fuel cells connected in series. The fuel cells may be designed in tubular form or as plates, a fuel cell module including fuel cells in plate form also being referred to as a fuel cell block.
In a fuel cell, electrical energy and heat are generated by bringing together hydrogen (H2) and oxygen (O2) in an electrochemical reaction, the hydrogen (H2) and oxygen (O2) combining to form water (H2O). For this purpose, hydrogen is introduced into the anode gas space of the fuel cell and oxygen is introduced into the cathode gas space of the fuel cell. The hydrogen can be fed into the fuel cell either as pure hydrogen or as a hydrogen-containing fuel gas. The oxygen can be fed to the fuel cell as pure oxygen or, for example, in the form of air.
When designing a fuel cell module, it should be ensured that the anode gas spaces and the cathode gas spaces of the module are connected to one another in such a manner that neither of the two operating gases can escape from the fuel cell module. Therefore, in the past highly evolved joining and connecting techniques have been developed, the intention being to ensure that neither of the operating gases escapes from a fuel cell module, this being undesirable.
During operation, the individual cells of a fuel cell module are subject to considerable temperature fluctuations. Moreover, the operating gases are passed into the module at a superatmospheric pressure. This superatmospheric pressure may amount to up to a few bar.
On account of the pressure and temperature fluctuations, the connections between individual fuel cells and the connections between the individual components of a fuel cell, such as for example an interconnecting conductor plate and a membrane-electrolyte assembly, are subject to particularly high demands. Therefore, leaks constantly occur in a fuel cell block, with the result that hydrogen or oxygen escapes from the fuel cell block into the environment. Since an escape of hydrogen entails a risk of explosion and even an escape of oxygen entails an increased risk of fire, it is imperative to prevent operating gases from escaping from a fuel cell module into the environment.